JPH09174960A - Printer controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the system performance by performing the expansion/ compression through simple circuitry thereby reducing burden on the software and hardware of expansion/compression processing using a general compression algorithm. SOLUTION: A compressing section 10 deletes the dot data of specific pattern in a dot image data stored in a page memory 81. A data indicative whether the dot data constituting a dot image is deleted at the compressing section or not is then stored on a map table 82 and the dot image data is compressed. A transfer control section 11 performs video DMA transfer of undeleted dot data based on the data stored on the map table 82.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer controller, and more particularly to compression of dot image data and transfer of compressed data.

[0002]

2. Description of the Related Art In a page printer, in order to secure a page memory for storing dot image data for one page, for example, about 4 MB for A3 paper 400 dpi, A3
A 600 dpi paper required a storage capacity of about 8 MB and required a large capacity RAM. For this reason, the controller of the page printer has become expensive. Therefore, an inexpensive controller was developed by compressing the dot image data in the page memory to reduce the capacity of the page memory.

As a method of compressing the dot image data in the page memory, a method of using a general compression algorithm has been adopted.

[0004]

However, when performing compression / expansion by software using a general compression algorithm, the load on the CPU is large and the system performance is deteriorated. On the other hand, when the compression / decompression process using a general compression algorithm is performed by hardware, the cost is increased by that hardware, and at the same time, the load of hardware development is large.

Further, since the video DMA transfer is generally performed by the video transfer word, if the dot image data compressed by the page memory compression method is transferred, the occupation rate of the system bus related to the video DMA transfer is increased. Cannot be lowered.

The present invention has been made in order to solve the above disadvantages, and it is possible to reversibly compress dot image data with a simple structure and to reduce the system bus occupation rate by DMA transfer, thereby improving the system performance. The purpose is to improve.

[0007]

A printer controller according to the present invention has a page memory, a compression unit, a map table and a transfer control unit, the page memory stores dot image data, and the compression unit stores it in the page memory. Data that indicates whether or not each dot that makes up the dot image in the map table has been deleted by the compression unit by deleting the dot data of a specific pattern from the dot image data The transfer controller stores the data of the undeleted dots in the print unit based on the data stored in the map table.
MA transfer.

Further, there is a program transfer section for transferring the dot image data to the printing section by a protocol under program control according to the control of the transfer control section, and the transfer control section is deleted based on the data stored in the map table. The dot pattern data is generated, the generated data is program-transferred, and the compressed dot image data is expanded.

Further, the transfer control unit has a pattern register for storing the data of dots of a specific pattern to be deleted, and the transfer control unit, based on the data stored in the map table, stores the dots stored in the pattern register as the data of the deleted dots. Data is transferred by a program to expand the compressed dot image data.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The printer controller of the present invention is used, for example, in a printer device or the like and develops dot data of print data received from an external host device or the like in a page memory and transfers it to a printing unit for printing. Therefore, paying attention to the fact that a specific pattern often appears in the dot image data expanded in the page memory, the dot data of the specific pattern in the dot image data stored in the page memory is deleted and the dot image is deleted. It has a function of compressing data. Further, according to the present invention, when the dot image data compressed by the printer controller having the above-mentioned function is transferred to the printing section by video DMA, the system bus occupation rate by the DMA transfer is reduced to improve the system performance.

The printer controller of the present invention has, for example, a page memory, a compression section, a map table, and a transfer control section. The page memory stores the dot image data transferred to the printing section. The compression unit deletes dots of a specific pattern from the dot image data stored in the page memory to compress the dot image data. Further, the compression unit sets the bit of the map table to "0" and the other bits to "1" corresponding to the dot from which the data is deleted. The specific pattern means, for example, a white dot.

The map table stores data indicating whether or not each dot forming a dot image has been deleted by the compression unit. The transfer control unit uses the data stored in the map table to execute the DMA
It is a part for controlling whether to transfer or program transfer, and includes a DMA transfer part and a program transfer part. The transfer control unit controls the data of the dots that have not been deleted to be transferred by video DMA. The DMA transfer unit performs video DMA transfer of the dot data forming the dot image to the printing unit under the control of the transfer control unit.

Further, the transfer control unit generates data of the deleted pattern for the dot whose data has been deleted, controls the generated data to be transferred by the program transfer unit, and compresses the dot image. Decompress the data. As a result, even if the data deleted during compression is not the data for the white dots, the data of the deleted dots can be supplemented and transferred. Note that the program transfer here means transfer by a communication protocol under program control.

Specifically, for example, it has a pattern register for storing the data of the pattern of a specific dot to be deleted, and the transfer control unit uses the data of the dot pattern stored in the pattern register as the data of the deleted dot. The compressed dot image data is expanded by controlling the program transfer.

[0015]

1 is a block diagram of a printer device 1 equipped with a printer controller according to an embodiment of the present invention. The printer controller 3 expands the print data received from the external host device 2 into a dot image, transfers it to the printing unit 4, and prints it.
5, font ROM6, non-volatile RAM (hereinafter "N
VRAM ”. ) 7, RAM 8, CPU 9, compression unit 10, transfer control unit 11, engine interface 12
And a host interface 13.

The ROM 5 stores a system program and control data for controlling the operation of the printer controller 3 as a whole. The font ROM 6 stores fonts. The NVRAM 7 stores print data and the like received from the host device 2 and the like. Further, the NVRAM 7 includes a pattern register 71 which is an area for storing data of a pattern of a specific dot to be deleted, for example. RAM8
Is a portion for temporarily storing data, and includes respective storage areas of a page memory 81 and a map table 82. The page memory 81 is, for example, as shown in FIG.
This is an area for storing dot image data composed of the matrix of (n). The map table 82 is composed of, for example, a (k) × (n) matrix as shown in FIG. 3, and each dot forming the dot image is compressed by the compression unit 1.
Data indicating whether the data has been deleted by 0 is stored. The matrix of the page memory 81 and the matrix of the map table 82 have a relationship of m <k so that the map table 82 does not overflow. The transfer buffer 83 stores the data to be transferred by the video DMA.

The CPU 9 controls the overall operation of the printer controller 3 based on the system program stored in the ROM 5. The compression unit 10 deletes the dot data of a specific pattern from the dot image data stored in the page memory 81 and compresses the dot image data. The specific pattern is specified by the compression unit 10 by referring to the data stored in the pattern register 71, and means, for example, a white dot. This is because when the white dots are deleted and compressed, the data of the dots may be skipped and sent without affecting the printed image. Further, the compression unit 10 sets the bit to “0” and the other bits to “1” in the map table 82 corresponding to the deleted data.

The transfer control unit 11 is a unit for controlling whether to perform DMA transfer or program transfer based on the map table 82, and includes a DMA transfer unit 111 and a program transfer unit 112. The transfer control unit 11 reads out the data of the dots that have not been deleted from the page memory 81, sets them for video DMA transfer, and transfers them from the DMA transfer unit 111 by video DMA. Further, the transfer control unit 11 generates deleted data for a dot whose data has been deleted, sets the generated data for program transfer, and transfers the program from the program transfer unit 112. The DMA transfer unit 111 performs video DMA transfer of the dot image data to the printing unit 4 via the engine interface 12.
The program transfer unit 112 is the engine interface 1
Dot image data to the printing section 4 via the video D
Transfer with a protocol under program control without MA transfer. The engine interface 12 and the host interface 13 send and receive data to and from the printing unit 4 and the host device 2, respectively.

First, a case will be described in which the data expanded in the page memory 81 is compressed by the printer interface 3 having the above configuration.

The print data received from the host device 2 is
After being expanded in the page memory 81 as shown in FIG. 4, all the corresponding bits of the map table 82 are set to "1".
Here, the data in the page memory 81 represents "1" dots in "32" bits, and the "1" bit in the map table 82 represents "1" dots in the page memory 81. Also, in the area 81b in the page memory 81 in the figure, the hatched dots are dots that are not white dots.

Consider a case where the dots in the area 81b in the page memory 81 are compressed. The compression unit 10 is a page memory 8
The dot data in the area 81b within 1 is sequentially read, the white dot data is deleted, and the bit of the map table 82 corresponding to the deleted dot is set to "0" as shown in FIG. By compressing in this way, in the map table 82, the bit corresponding to the dot for which data has been deleted becomes "0", and the bit corresponding to the dot for storing data in the page memory 81 becomes "1".

Next, the operation of decompressing the dot image data compressed as described above and transferring it to the printing unit 4 will be described with reference to the flowchart of FIG.

When the dot image data is expanded in the page memory 81, the transfer control unit 11 causes the DMA transfer unit 111.
Before starting the transfer by the map table read pointer (hereinafter,
It's called "wraddr". ), And the start address of the page memory 81 is set to the frame buffer read pointer (hereinafter referred to as “fraddr”) (step S).
1). When the transfer control unit 11 sets an address in the pointer, the transfer control unit 11 causes the map table 82 indicated by wraddr.
The "32" -bit data of is read out and the number of repetitions of the bit inspection is set to zero (step S2). The transfer control unit 11 reads the data “32” in the map table 82.
If the inspected bit is "0" (step S4), "32" bit "0" data is set as the program transfer target (step S5), and the inspected bit is "1". If it is, the "32" bit data is read from the address of the page memory 81 indicated by fraddr (step S6), and the read data is video DM.
A is set as a transfer target (step S7). afterwards,
The transfer control unit 11 shifts the data read from the map table 82 to the left by "1" bit, increments the pointer of fraddr, and prepares for the inspection of the next bit (step S8). The transfer control unit 11 repeats the above bit inspection “32” times (step S9) and sequentially inspects all the bits of the data read from the map table 82.

Thereafter, the transfer control unit 11 increments wraddr (step S10), and the above operation (step S10).
2 to S10) are repeated until the processing is completed by the number of times of video transfer (step S11). In this way, the printer controller 3 can expand the dot image data compressed by the compression unit 10 as shown in FIG.

Although the white dot data is deleted in the above embodiment, the frequently appearing dot data is stored in the pattern register 71 in advance and compressed, and the data stored in the pattern register 71 is replenished when the data is expanded. You may do it.

Further, the dot image data in the page memory 82 may be examined before the above-mentioned processing, and the data of frequently appearing dots may be stored in the pattern register 71.

[0027]

As described above, according to the present invention, the dot data of a specific pattern in the dot image data stored in the page memory is deleted, the dot image data is compressed, and the dot image data is transferred by video DMA. When doing the video DM with the data of the dots that have not been deleted
Since the A transfer is performed, the dot image data can be reversibly compressed, the data amount of the video DMA transfer can be reduced, and the occupation rate of the system bus by the video DMA transfer can be reduced.

Further, since the system bus occupation rate due to the video DMA transfer can be reduced, the system performance can be improved.

Further, when the dot data to be transferred is deleted, the deleted dot pattern data is generated, and the generated data is video DM.
Since the compressed dot image data is expanded by program transfer without A transfer, the occupation ratio of the system bus by the video DMA transfer can be reduced and the compressed dot image data can be easily expanded. .

Further, when the dot data to be transferred is deleted, the data of the dot pattern to be deleted stored in the pattern register is recorded in the video D.
Since the compressed dot image data is expanded by program transfer without MA transfer, data of an arbitrary pattern can be deleted and replenished for compression / expansion processing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of dot image data.

FIG. 3 is a configuration diagram of a map table.

FIG. 4 is a configuration diagram of dot image data and a map table before compression.

FIG. 5 is a configuration diagram of dot image data and a map table after compression.

FIG. 6 is a flowchart showing an operation of a DMA transfer preprocessing.

FIG. 7 is a configuration diagram of dot image data and a map table after decompression.

[Explanation of symbols]

 1 printer device 2 host device 3 printer controller 4 printing unit 71 pattern register 81 page memory 82 map table 10 compression unit 11 transfer control unit 111 DMA transfer unit 112 program transfer unit

Claims (3)

[Claims] 1. A page memory, a compression unit, a map table, and a transfer control unit are provided, the page memory stores dot image data, and the compression unit stores dots of a specific pattern in the dot image data stored in the page memory. The data is deleted and the dot image data is compressed, and the map table stores data indicating whether or not each dot forming the dot image has been deleted by the compression unit, and the transfer control unit stores it in the map table. A printer controller which performs video DMA transfer of dot data that has not been deleted based on the created data. 2. The printer according to claim 1, wherein the transfer control unit generates the data of the deleted dot pattern based on the data stored in the map table, and transfers the generated data by program transfer without video DMA transfer. controller. 3. A pattern register for storing dot data of a specific pattern to be deleted, and the transfer control unit, based on the data stored in the map table, the dot stored in the pattern register as the data of the deleted dot. 3. The printer controller according to claim 2, wherein the program data is transferred without the video DMA transfer.